Ban, due to visit the country on Thursday, was unable to get Than Shwe, Myanmar's senior general, to even accept his telephone calls in the aftermath of Cyclone Nargis, which has left at least 133,000 people dead or missing.

Than Shwe made his first public appearance since the disaster, shown on state television in Yangon on Monday.

The reclusive leader was shown inspecting water supplied for cyclone-victims and meeting ministers involved in the relief operations.

The UN believes 2.4 million people are still short of aid 17 days after the tragedy struck.

Relief agencies have warned that the most vulnerable survivors will start dying soon unless they get the aid they need.

'Huge challenge'

The UN has said only a fraction of the emergency supplies needed have got through to people in the Irrawaddy Delta, where whole villages were swept away when Cyclone Nargis hit on May 2-3.

"This is not of the quantity or frequency required to meet the needs of the affected populations," it said in its daily update, adding that hungry survivors were migrating out of their villages in search of food.

Ministers at the Asean talks in Singapore observed a minute's silence in remembrance of the victims of Asia's twin tragedies this month - the Myanmar cyclone and last week's devastating earthquake in China.